1. Technical Field
The invention relates generally to metrology in a manufacturing environment, and more particularly, to a method and system of providing a dynamic sampling plan for integrated metrology (IM) associated with a wafer manufacturing process tool.
2. Background Art
Manufacturers, especially semiconductor fabricators, who implement advanced process control (APC) systems, generally do so at the factory level. APC systems take measurements of particular structures before and after a processing step and provide corrections to recipes for feeding forward and/or feeding back to tools to achieve a better product. FIG. 1 shows a typical semiconductor fabricator environment 10 including a number of tools 12, a manufacturing execution system (MES) 14 that controls all product movements through environment 10, e.g., it schedules product movements, and an equipment interface (EI) 18 that interfaces between MES 14 and different tools 12. Although not shown, middleware may be present for communication between MES 14 and EI 18. Each tool 12 includes process equipment, or process chambers 20 particular to its function, e.g., an etching chamber, gas source, appropriate electronics, etc., in the case of an etching tool 12.
One of the steps in wafer manufacturing is measurement or metrology. Metrology may be provided by an external metrology tool (not shown) or an integrated metrology (IM) module 22 associated with a particular process tool 12. Providing sampling plans to external metrology tools has been a subject of several inventions. The next challenge lies in providing a dynamic sampling plan for an IM module 22.
An increasing number of prominent tool vendors are developing an IM module 22 as part of the tools 12. The IM module 22 may be configured and used either for pre- or post-measurement. Currently, the only method of using a sampling plan is to hard code a sampling plan into the EI 18 and pass it directly to IM module 22. This method has shortcomings due to the inflexibility of IM module 22. For example, IM module 22 can only be turned on to measure every wafer; turned off so as to measure no wafers; or, only measure wafers having a fixed frequency (which is typically based on a particular slot position of a front opening unified pod (FOUP) 24). However, because in some cases the particular slot in the FOUP 24 may be empty, the method is rendered ineffective. Further, a problem arises because, typically, there are multiple process chambers 20 and only one IM module 22 in a process tool 12. This ultimately leads to a bottleneck in the throughput of the tool 12.
In view of the foregoing, a need exists to overcome one or more of the deficiencies in the related art.